omega-Grammotoxin SIA (ω-grammotoxin SIA) is a protein toxin that inhibits P, Q, and N voltage-gated calcium channels (Ca2+ channels) in neurons.
The source of ω-grammotoxin SIA is the venom of a tarantula spider (Grammostola rosea).
Amino acid sequence: Asp-Cys-Val-Arg-Phe-Trp-Gly-Lys-Cys-Ser-Gln-Thr-Ser-Asp-Cys-Cys-Pro-His-Leu-Ala-Cys-Lys-Ser-Lys-Trp-Pro-Arg-Asn-Ile-Cys-Val-Trp-Asp-Gly-Ser-Val[1] Molecular formula: C177H268N52O50S6[1] ω-Grammotoxin SIA can be purified from Grammostola rosea venom by reverse phase high performance liquid chromatography.
[2] ω-Grammotoxin SIA is a 36 amino acid residue protein toxin from spider venom that inhibits P, Q, and N-type voltage-gated calcium channels in neurons.
[3] The toxin binding site has high affinity when channels are in closed states and low affinity when channels are activated.